The pattern pieces below that I drafted are the equivalent to a pattern size 5, with a 24 inch chest. In ready-to-wear-sizing I would put the sizing at about a girls size 7/8 (children are growing like weeds around here!).
You are going to need to make a circle skirt that is the length of the bottom of your bodice. If you are using the pattern pieces above, the radius for the top of your circle skirt is going to be 3.8 inches (I just cut a little further than the 3.75 inch line on my tape measure and it worked perfectly.)